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Effects of two recovery methods on the leg muscle fatigue of oceanauts in a manned submersible

100%
Chen D., Zhu M., Fan Y., Wang J.
Medycyna Pracy
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2022
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vol. 73
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issue 2
95-107
EN
The cabin of the manned submersible is a narrow and sealed space. The long-time work of oceanauts is easy to cause muscle fatigue and stiffness, which reduces efficiency. This paper explored the relative more effective way to relieve leg muscle fatigue of the oceanauts in the manned submersible.Material and MethodsTwenty healthy young people with an average age of 24 years were selected as the participants, while the usual natural relaxation and the stretching method proposed by the surveys were selected as the relieve method for muscle fatigue. This study compared the effects of the 2 recovery ways using the electromyography data from the quadriceps femoris and biceps femoris, and the subjective scales.ResultsWith the support of data of integral electromyogram (iEMG), root-mean-square (RMS), subjective scales, authors finally found that the 2 muscles of the leg are fatigued significantly, and biceps femoris has more accumulation of fatigue. Although the 2 recovery ways have a significant relief effect on muscle fatigue, the stretching method can reduce more muscle fatigue in a short period of time, especially for biceps femoris. The stretching method is advocated for the oceanauts.ConclusionsThe findings suggested that the stretching method was optimal for relieving the muscle fatigue of the oceanauts during the operation. Med Pr. 2022;73(2):95–107
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A method for designing the longitudinal position of a porthole in a manned submersible based on the back muscle fatigue characteristics

100%
Zhu M., Chen D., Fan Y., Guo J.
International Journal of Occupational Medicine and Environmental Health
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2021
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vol. 34
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issue 6
701-721
EN
ObjectivesThe proper porthole angle contributes to relieving the operation fatigue and improving the efficiency of oceanauts. In this study, the authors explored the effect of 3 different porthole longitudinal positions on the oceanauts’ back muscles using surface electromyography (sEMG) analysis, and the characteristics of the perceived body comfort was obtained.Material and MethodsOverall, 40 healthy participants were recruited to perform tasks in a simulated cabin environment. Electromyographic (EMG) signals were recorded from the trapezius medius, lower trapezius, and erector spinal muscles for porthole angles of –5°, –15°, and +15°, relative to the horizontal line of sight during a 21-minute experiment. The subject comfort scores were collected at 7, 14 and 21 min. The integrated electromyogram (iEMG) and the root mean square (RMS) of EMG signals, as well as the mean power frequency (MPF), and the mean frequency (MF) were calculated.ResultsThe subjective scores of the +15° porthole at each stage of work are higher than those of the –15° and –5° portholes. The results of iEMG, RMS, MF and MPF all indicated that the +15° porthole design was more conducive to lowering the rate of muscle fatigue, while the –5° and –15° portholes increased the muscle fatigue rate and led to greater fatigue. It was found that the lower trapezius was more prone to fatigue than the trapezius medius and erector spinal muscles. The height, weight and body mass index of the participants were found to negatively correlate with muscles at the +15° porthole, which is highly consistent with the actual situation.ConclusionsThe findings suggested that the +15° position was optimal for delaying the muscle fatigue of the participants and for improving the work efficiency of oceanauts.
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